Comparison of the Transperitoneal and Retroperitoneal Approach in Robot-Assisted Partial Nephrectomy in an Initial Case Series in Japan

Abstract

Purpose:

To compare the results from the transperitoneal and retroperitoneal approaches in our initial case series of robot-assisted partial nephrectomy (RAPN) in terms of surgical time, renal artery clamping time, postoperative renal function, adverse events, and surgical margin status.

Patients and Methods:

The initial 26 consecutive RAPNs performed for solid renal tumors in our hospital were categorized by the approach used, transperitoneal or retroperitoneal, and compared for body mass index, tumor size, R.E.N.A.L. nephrometry score, PADUA score, tumor location, surgical time, renal artery clamping time, renal function change after surgery, operative blood loss, surgical margin status, and adverse events (AEs).

Results:

The median tumor size was 25 mm (range 15–50). A transperitoneal approach was used in 16 patients and a retroperitoneal approach was used in 10 patients. There was no significant difference in renal tumor and patient characteristics between the two groups except tumor location (anterior tumor was significantly more in the transperitoneal approach and posterior tumor was significantly more in retroperitoneal approach (P=0.0144 and P=0.0100, respectively)). Operative time (239±63.0 minutes in the transperitoneal group vs. 193±40.6 minutes in the retroperitoneal group), warm ischemic time (24.3±9.07 minutes in the transperitoneal group vs. 24.7±8.35 minutes in the retroperitoneal group) and AEs (1/16 in the transperitoneal group vs. 1/10 in the retroperitoneal group; both cases were Clavien-Dindo grade I) did not show any significant difference between the two approaches (P=0.0792, 0.5485, and 0.7270, respectively).

Conclusions:

The retroperitoneal approach in RAPN appears to be a safe and technically feasible minimally invasive option for nephron-sparing surgery, based on our initial case series, and showed equivalent outcomes to those of the transperitoneal approach even though it was an initial robotic renal surgery series. Future studies, including a larger number of cases, are planned to draw more definitive conclusions.

Introduction

The incidental detection of localized renal tumors has increased over the past several decades. More than 60% of renal masses detected each year are <4 cm.¹ Nephron-sparing surgery for small renal masses achieves excellent functional and oncological outcomes.² Robotic technology offers the potential advantages of high definition three-dimensional (3D) vision, a greater range of wristed-instrument motion, and fine scaling of surgical movements. The use of robotics may facilitate minimally invasive partial nephrectomy (PN), and robot-assisted PN (RAPN) may have a shorter learning curve than laparoscopic partial nephrectomy (LPN).³

In RAPN, the transperitoneal approach is considered common,⁴ and the retroperitoneal approach is thought to be more technically challenging because of the smaller operative space.⁵ The retroperitoneal approach is common in open PN⁶ partly because the comparatively lower stress to patients.⁷ Recently, Patel and Porter⁸ reported a comparatively large scale study of the retroperitoneal approach in RAPN in a high-volume center after a many case experience of using the transperitoneal approach in RAPN, and showed feasibility. In this situation, as in our institution, it may be necessary to see whether the retroperitoneal approach in RAPN could be performed even by surgeons early in their robotic learning curve.

This study compared the results from the transperitoneal and retroperitoneal approaches in RAPN in our initial case series in terms of surgical time, renal artery clamping time, postoperative renal function, adverse events (AEs), and surgical margin status.

Patients and Methods

Our initial case series included a total of 26 consecutive planned RAPNs performed at this institution with the da Vinci S surgical system (Intuitive Surgical, Sunnyvale, CA) from June 2011 to January 2013. The bedside assistant used a 3D monitor system (3D Control Unit; SkyJet, Kobe, Japan) to share 3D visualization with the console surgeon. The procedures were performed by a single surgeon with experience in performing 26 cases of robotic-assisted radical prostatectomy at the time of the initiation of this study. The surgeon also had performed 32 cases of LPNs, 29 of which were performed using the retroperitoneal approach. The patient data were entered prospectively into the institutional review board-approved RAPN database.

Surgical procedure

A three-arm technique was used in both the transperitoneal and retroperitoneal approaches.⁹ The retroperitoneal approach was used throughout the study period. The patient was placed in the lateral decubitus position. A fourth and fifth trocar were placed to facilitate retraction and suction by the assistant for procedures using either approach. A sixth 5-mm trocar was occasionally placed for liver traction in right-sided cases. The bowel was mobilized medially, and the renal hilum was identified. The perinephric fat was then cleared circumferentially around the tumor to allow clear visualization of the dissection margin and provide a clear view of the tumor capsule for subsequent reconstruction. The fat overlying the tumor was left for retraction. A laparoscopic ultrasound probe was used to decide the excision margins. The renal parenchyma was scored with an electrocautery device, maintaining a visual 0.5-cm tumor margin, and approximated by placing sutures through the capsule with 30 cm 2-0 V-Loc on a GS-21 needle without using the sliding clip technique.

The tumor was excised sharply with a rim of normal renal parenchyma. The collecting system and large vessels were closed with 15 cm 3-0 V-Loc sutures using a V-20 needle. Bulldog clamps were placed on renal artery or the tumor-specific arterial branches to selectively devascularize the tumor. The assistant inserted an entrapment bag and the tumor was then extracted. In the retroperitoneal approach, in detail, one 2-cm incision was made at the midaxillary line halfway between the lower costal margin and the iliac crest. The retroperitoneal space was entered under direct vision and a balloon expansion of the retroperitoneal working space was performed. After complete expansion, the first trocar was inserted as a camera port. Next, the second and third da Vinci ports were created for the da Vinci left and right hand at 8 cm apart from the camera port. Then a fourth port with an incision of 12 mm in diameter was placed at 2–3 cm medially from the spina iliaca anterior superior for the assistant. The da Vinci robotic surgical system was docked from the patient's cephalad side. Other procedures were the same as the transperitoneal approach.

Preoperative evaluation of renal artery and tumor localization was performed using the Osirix software package and a detailed 3D road map was constructed from CT images. The reconstructed 3D images were projected onto the console screen with TilePro to confirm the correct feeding artery branches.

Follow-up data were obtained from medical records and outpatient visits. All complications within 30 days of surgery were considered related to the surgery and were graded according to the 2004 Clavien-Dindo grading system.¹⁰

Comparison between the transperitoneal and retroperitoneal approaches in RAPN

Preoperative factors, such as patient characteristics, tumor size, operation-related factors, postoperative renal function maintenance, AEs, and margin status were compared between the transperitoneal and retroperitoneal approaches.

Statistical analysis

Statistical analyses were performed using the Student t-test or the chi-square test for univariate analysis with P<0.05 considered to indicate statistical significance. Tests were performed with JSTAT (Java Virtual Machine Statistics Monitoring Tool, Oracle Corporation, Redwood City, CA).

Results

Patient characteristics and renal tumor details

Patient characteristics and renal tumor details are shown in Table 1. Twenty-six RAPNs with full data for evaluation were completed robotically except for one case that was converted to laparoscopic nephrectomy because of finding a grossly positive surgical margin during RAPN. The transperitoneal approach was used in 16 cases and the retroperitoneal approach was used in 10 cases. There were no statistically significant differences in tumor size, R.E.N.A.L. nephrometry¹¹ or PADUA scores¹² between the two groups (P=0.0534, 0.7777, and 0.6966, respectively). In addition, there was a significant trend toward more anterior tumors in the transperitoneal group (P=0.0144) and more posterior tumors in the retroperitoneal group (P=0.0100) (Table 1).

Table 1.

Patients' Backgrounds

	Transperitoneal (n=16)	Retroperitoneal (n=10)	P-value
Age	70 (35–84)	60.5 (46–82)	0.7690
Sex
Male	11	8	0.5292
Female	5	2
Site
Right	12	7	0.7798
Left	4	3
BMI	22.7±2.94	23.2±2.23	0.6038
Tumor size (mm)	33.6±11.0	22.1±5.55	0.0534
R.E.N.A.L. nephrometry score	7.4±1.65	6.9±1.29	0.7777
PADUA	8.8±1.55	8.4±1.08	0.6966
Tumor location
Anterior	7	0	0.0144^a
Posterior	1	5	0.0100
Latera1	6	2	0.3469
Medial	2	3	0.2707

Statistically significant.

BMI=body mass index; R.E.N.A.L.=(radius; exophytic/endophytic; nearness; anterior/posterior; location).

Operation-related factors

Operation-related factors were compared between the two RAPN groups (Table 2). Operative time tended to be less in the retroperitoneal group but this difference did not reach statistical significance (P=0.0792). Warm ischemia time (WIT) was 24.3±9.07 minutes in the transperitoneal approach and 24.7±8.35 minutes in the retroperitoneal approach (P=0.5485).

Table 2.

Operation and Pathology

	Transperitoneal (n=16)	Retroperitoneal (n=10)	P-value
Surgical time (minutes)	239±63.0	193±40.6	0.0792
Arterial clamping time (minutes)	24.3±9.07	24.7±8.35	0.5485
Pathology			0.2707
Malignancy (renal cell carcinoma)	14 (87.5%)	7 (70%)
Benign	2 (12.5%)	3 (30%)
Angiomyolipoma	1	2
Inflammatory myofibroblastic tumor	1	1
Oncocytoma	0	0
Estimated blood loss (mL)	33±41.1	13.5±7.47	0.114
Positive surgical margin	0/16	1/10^a	0.1971
Adverse events	1 (grade^b IIIa. AMI)	1 (grade I. superficial SSI)	0.7270

Positive surgical margin: A pT3 tumor case with a grossly positive surgical margin found during RAPN was converted to laparoscopic nephrectomy.

Clavien-Dindo grading.

AMI=acute myocardial infarction; SSI=surgical site infection; RAPN=robot-assisted partial nephrectomy.

Adverse events

AEs were seen in 1/16 (Clavien-Dindo grade III, acute myocardial infarction [AMI]) patients in the transperitoneal group and 1/10 (grade I, superficial surgical site infection [SSI]) cases in the retroperitoneal group (P=0.7270). All these cases with AEs recovered in a reasonable time course (Table 2).

Pathologic findings

Pathologic findings are shown in Table 2. A pT3 tumor was included in the retroperitoneal approach group and a grossly positive surgical margin was found during RAPN resection; the procedure was converted to laparoscopic nephrectomy. Clear cell renal cell carcinoma was seen in 14/16 (87.5%) patients in the transperitoneal approach group and 7/10 (70%) in the retroperitoneal approach group (P=0.2707) (Table 2).

Postoperative renal function

The renal function data are presented in Table 3. No significant change in estimated glomerular filtration rate (eGFR) from preoperative data was seen in either group at 1 week, 1 month and 3 months postoperatively (P>0.05) In addition, no significant eGFR change from preoperative data to those of 3 months postoperatively was seen in either group (P>0.05).

Table 3.

Renal Function Change

	Transperitoneal (n=16)	Retroperitoneal (n=10)	P-value ^a
Preoperative eGFR	74.2±16.7	69.7±18.4 (P=0.8720)^b
eGFR at 7POD	65.0±14.6	59.6±16.2	0.501
eGFR at 1POM	67.2±16.4	65.4±16.1	0.482
eGFR at 3POM	64.6±15.1 (P=0.2530)^c	59.1±15.1 (P=0.1904)	0.176

Comparison of eGFR change from preoperative data between two approaches.

Comparison of preoperative eGFR data between two approaches.

Comparison of eGFR change between preoperative and 3POM data.

eGFR=estimated glomerular filtration rate; POD=postoperative day; POM=postoperative month.

Discussion

Nephron-sparing surgery has become the preferred method of management for small renal tumors, offering complete tumor extirpation with maximal preservation of renal function. Although experience is still limited, the emerging technique of RAPN has demonstrated early outcomes comparable to those of open and traditional laparoscopic approaches.^13,14 One of the most important outcomes we should pay attention to is the free positive surgical margin rate.¹⁵ The frequency of positive margins in nephron-sparing surgery ranges from 1.2% to 5.8% in the literature.^16

–21 A large open PN series that included 1390 procedures reported by Yossepowitch and associates¹⁶ identified a 5.8% positive margin rate, and other series have ranged from 1.8% to 3.5%. Positive surgical margin rates have ranged from 1.2% to 5.7% in other relatively large RAPN series.^20,21 These rates are comparable to those for open and LPN. Our RAPN data showed 3.8% (1 of 26 cases) positive surgical margin findings during RAPN, and this procedure was converted to laparoscopic nephrectomy because the hilar tumor needed to be removed. We interpreted this case as follows: (1) The tumor location was the renal hilus; (2) the tumor size was comparatively large (35 mm in the longest diameter), and the peripheral renal artery ran just along the tumor so the tumor and the artery were not fully detached; (3) therefore, not enough surgical margin could be taken apart from the tumor.

One feature to be emphasized in RAPN is maintaining renal function after the tumorectomy and suturing, which has a steep learning curve in LPN.¹⁴ Renal ischemia during these procedures is the main surgeon-dependent risk factor affecting the functional outcomes of PN.²² Benway and colleagues¹⁴ found a substantial reduction in WIT, from 28.4 minutes overall in the LPN group to 19.7 that minutes overall in the RAPN group. This 30% reduction in study represents perhaps the most important parameter that differed between the groups.¹⁴ Our initial case series data showed similar results of 24 minutes of WIT in both the transperitoneal and retroperitoneal approach groups, suggesting that RAPN offers safe surgery even with naïve surgeons (in our series, the surgeon had previously performed only 26 cases of robot-assisted radical prostatectomy).

Preoperative imaging of renal tumors and tumor connections with vessels reveals individual variations in hilar renovascular anatomy, and thus, a renal CT (0.5 mm slices) and reconstruction of detailed 3D images facilitates the identification of tumor-specific vessels. Reconstructed 3D images with TilePro projection onto the console screen allow the surgeon to identify even the second and third branches.²³ Anatomic microdissection of renal artery branches can be delicately performed robotically,²⁴ and these imaging evaluations before surgery could be informative for recognition of tumor location and its relationship with the renal artery.

Debate persists about whether the transperitoneal or retroperitoneal approach to the kidney is better in RAPN.^25,26 In general, patients with posterior tumors were selected for the retroperitoneal approach based on data in previously published articles.^26,27 This approach has the benefit of easier handling of renal vessels than with the transperitoneal approach.²⁶ There was no significant difference in WIT or estimated blood loss between the transperitoneal and retroperitoneal approaches in our cases. Operative time tended to be shorter with the retroperitoneal approach but this was not statistically significant (P=0.0792). We may increase the use of the retroperitoneal approach in future cases, especially in patients with a history of abdominal surgery via the transperitoneal approach. In addition, our results concerning tumor location showed that the transperitoneal approach was used more for anterior tumors, and the retroperitoneal approach more for posterior tumors, suggesting that the retroperitoneal approach may be indicated for posterior tumors. Although a larger scale study from a high-volume center performing RAPNs via the retroperitoneal approach should be considered,⁸ our study of an initial case series may demonstrate that a retroperitoneal approach can be feasible even for surgeons early in their robotic learning curve.

Regarding AEs, Patel and Porter⁸ had three (4.4%) cases of pseudoaneurysms in their 68 cases using the retroperitoneal approach in RAPN. As an initial case series, Gettman and coworkers⁹ had one (7.7%) case of ileus in 13 RAPN cases. Our initial 26 RAPN cases included two AEs (AMI and superficial SSI), but all patients recovered, and there were no pseudoaneurysms. The percentage of AEs might be expected to decrease with increased experience.

We would like to emphasize our study limitations. First, the number of RAPN cases was not large enough to draw definite conclusions. RAPN is not yet covered by government medical insurance in Japan. Once coverage begins, the number of RAPN cases will increase. Second, the postsurgical follow-up in this RAPN case series is not long enough to evaluate oncologic outcomes, such as tumor recurrence or metastasis. Third, this study is retrospective, and several variations of tumor location and size are included, for instance, our challenging case with conversion to nephrectomy (35 mm diameter tumor with a renal hilar location). Future prospective studies may have more definitive indications for RAPN. Our comparison between the transperitoneal and retroperitoneal approach in our initial consecutive case series however, should be of interest to surgeons who are about to start RAPN.

Conclusions

RAPN appears to be a safe and technically feasible minimally invasive operation for nephron-sparing surgery based on our initial case study. The operative time, arterial clamping time, positive surgical margin ratio, and AEs showed acceptable outcomes in both the transperitoneal and retroperitoneal approach groups. Further studies with a greater number of cases will provide a more definitive assessment of the efficacy of RAPN.

Footnotes

Acknowledgment

We thank Dr. Fukashi Yamamichi for drafting the article.

Disclosure Statement

No competing financial interests exist.

Abbreviations Used

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